HYDATIFOBM DEGENERATION IN TUBAL AND UTERINE PREGNANCY. 353 



the two. Nor do I believe that the assumption that syncytium can resolve itself 

 into individual cells can be used to deny the implication of these facts. 



Although hydatiform villi covered by a single layer of rather small cells of the 

 nature of Langhans cells, sometimes without visible cell boundaries, frequently 

 were seen, villi covered by typical syncytium only never were seen. The single 

 layer present, although syncytial in places, suggested Langhans cells rather than 

 the real syncytium. Moreover, since the cells of the Langhans layer usually were 

 smaller rather than larger than normal, it follows from this alone that their pro- 

 liferation must have been marked, in order to completely cover the enlarged villus, 

 in spite of the fact that the layer remained single-celled. Were this not the case, 

 the extraordinary increase in size which accompanies the formation of large hydatid 

 cysts could not possibly occur without rupture of the covering layer. 



Not infrequently proliferation of the epithelium without increase in thickness 

 may manifest itself in another way. The caliber of the villi in the earlier stages of 

 hydatiform degeneration sometimes does not increase much, no thickening of the 

 proliferating epithelium is noticeable, and yet the latter shows marked proliferation. 

 Under these circumstances, the borders of the villi and of the chorionic epithelium 

 may appear extraordinarily sinuous as illustrated in figure 26, and epithelial invagi- 

 nations from opposite sides rarely meet in the center, as indicated in figure 27, and 

 by fusion completely isolate a portion of the stroma. It usually is in these cases of 

 very sinuous epithelium that the epithelial invaginations sometimes become con- 

 stricted, leaving a closed epithelial vesicle or a nodule of epithelium attached to a 

 stalk or wholly isolated within the stroma, as shown in figures 28 and 29. All 

 stages in this process of vesicle formation were found, and rarely also extensions of 

 epithelial sprouts as described by Neumann (1897) and others were seen, portions 

 of which had become isolated in the stroma to appear later as typical syncytial 

 giant cells. These facts, too, would seem to throw a sidelight upon the origin of the 

 syncytium for those to whom this question is still an open one. 



All these things abundantly testify to the activity on the part of the epithelium 

 in many hydatiform moles, even when thickening of it is absent, but they are of 

 diagnostic value only if present, and I wish to emphasize again that they may be 

 wholly absent or at least unrecognizable in the early stages. Moreover, the degree 

 of epithelial proliferation varies greatly, as illustrated in figures 30, 31, and 32. 



Until I am able to learn more about the structure of normal villi in various 

 stages of development, I am not willing to commit myself regarding the incipient 

 changes in hydatiform degeneration. These may be unrecognizable with present 

 methods. However, it is possible to say that in young conceptuses the disappear- 

 ance of the capillaries, which was regarded as a possible cause for the development 

 of hydatiform mole by Hewitt (1860 and 1861), and also emphasized later by Halm 

 (1865), Maslowsky (1882), and by others, undoubtedly is a very early and possibly 

 the very earliest noticeable change in some cases. Of course, I do not imply that 

 death of the embryo is the cause of this disappearance, as Hewitt held, and I am not 

 ready to say that the vascular change is the very earliest one in all cases. This 

 would imply that hydatiform degeneration under no circumstances can begin before 



